FEATURE: Try to load plugin gems platform variants (discourse#21643)

lib/plugin_gem.rb

@@ -9,10 +9,8 @@ def self.load(path, name, version, opts = nil)
     spec_path = gems_path + "/specifications"
 
     spec_file = spec_path + "/#{name}-#{version}"
-    spec_file += "-#{opts[:platform]}" if opts[:platform]
-    spec_file += ".gemspec"
 
-    unless File.exist? spec_file
+    unless platform_variants(spec_file).find(&File.method(:exist?)).present?
       command =
         "gem install #{name} -v #{version} -i #{gems_path} --no-document --ignore-dependencies --no-user-install"
       command += " --source #{opts[:source]}" if opts[:source]
@@ -21,15 +19,27 @@ def self.load(path, name, version, opts = nil)
       Bundler.with_unbundled_env { puts `#{command}` }
     end
 
-    if File.exist? spec_file
+    spec_file_variant = platform_variants(spec_file).find(&File.method(:exist?))
+    if spec_file_variant.present?
       Gem.path << gems_path
-      Gem::Specification.load(spec_file).activate
+      Gem::Specification.load(spec_file_variant).activate
 
       require opts[:require_name] ? opts[:require_name] : name unless opts[:require] == false
     else
       puts "You are specifying the gem #{name} in #{path}, however it does not exist!"
-      puts "Looked for: #{spec_file}"
+      puts "Looked for: \n- #{platform_variants(spec_file).join("\n- ")}"
       exit(-1)
     end
   end
+
+  def self.platform_variants(spec_file)
+    platform_less = "#{spec_file}.gemspec"
+
+    platform_full = "#{spec_file}-#{RUBY_PLATFORM}.gemspec"
+
+    platform_version_less =
+      "#{spec_file}-#{Gem::Platform.local.cpu}-#{Gem::Platform.local.os}.gemspec"
+
+    [platform_less, platform_full, platform_version_less]
+  end
 end